Top Expert Image Processing Interview Preparation Guide

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The range of values spanned by the gray scale is called dynamic range of an image. Image will have high contrast, if the dynamic range is high and image will have dull washed out gray look if the dynamic range is low.

A Color model is a specification of 3D-coordinates system and a subspace within that system where each color is represented by a single point.

The two types of light receptors are
• Cones and
• Rods

The hue of a perceived color depends on the adoption of the viewer. For example,the American Flag will not immediately appear red, white, and blue of the viewer has been subjected to high intensity red light before viewing the flag. The color of the flag will appear to shift in hue toward the red component cyan.

A digital image is composed of a finite number of elements each of which has a particular location or value. These elements are referred to as pixels or image elements or picture elements or pixls elements.

Transformation is used to alter the co-ordinate description of image.
The basic geometric transformations are
1. Image translation
2. Scaling
3. Image rotation

Mach band effect means the intensity of the stripes is constant. Therefore it preserves the brightness pattern near the boundaries, these bands are called as mach band effect.

When x, y and the amplitude values of f all are finite discrete quantities , we call the image digital image.

Gray level refers to a scalar measure of intensity that ranges from black to grays and finally to white.

Path from pixel p with co-ordinates (x, y) to pixel q with co-ordinates (s,t) is a
sequence of distinct pixels with co-ordinates.
35. Give the formula for calculating D4 and D8 distance.
D4 distance ( city block distance) is defined by
D4(p, q) = |x-s| + |y-t|
D8 distance(chess board distance) is defined by
D8(p, q) = max(|x-s|, |y-t|).

The region reserved brightness not depend on its intensity but also on its background. All centre square have same intensity. However they appear to the eye to become darker as the background becomes lighter.

In each eye, cones are in the range 6-7 million and rods are in the range 75-150 million.

Brightness of an object is the perceived luminance of the surround. Two objects with different surroundings would have identical luminance but different brightness.

Machband effect means the intensity of the stripes is constant. Therefore it preserves the brightness pattern near the boundaries, these bands are called as machband effect.

Sampling means digitizing the co-ordinate value (x, y).
Quantization means digitizing the amplitude value.

Sampling means digitizing the co-ordinate value (x, y).Quantization means digitizing the amplitude value. Several rods are connected to one nerve end. So it gives the overall picture of the image.This is also known as thin lightvision.

Photopic vision Scotopic vision
1. The human being can resolve the fine details with these cones because each one is connected to its own nerve end.
2. This is also known as bright light vision.

Resolution is defined as the smallest number of discernible detail in an image.Spatial resolution is the smallest discernible detail in an image and gray level resolution refers to the smallest discernible change is gray level.

Image translation means reposition the image from one co-ordinate location to another along straight line path.
Scaling is used to alter the size of the object or image (ie) a co-ordinate system is scaled by a factor.

Shrinking may be viewed as under sampling. To shrink an image by one half, we delete every row and column. To reduce possible aliasing effect, it is a good idea to blue an image slightly before shrinking it.

Subjective brightness means intensity as preserved by the human visual system.Brightness adaptation means the human visual system can operate only from scotopic to glare limit. It cannot operate over the range simultaneously. It accomplishes this large variation by changes in its overall intensity.

1. Image Acquisition
2. Preprocessing
3. Segmentation
4. Representation and Description
5. Recognition and Interpretation

Image rectification is a transformation process used to project two-or-more images onto a common image plane. It
corrects image distortion by transforming the image into a standard coordinate system.

It is used in computer stereo
vision to simplify the problem of finding matching points between images.
It is used in geographic information systems to
merge images taken from multiple perspectives into a common map coordinate system.

Illumination is the amount of source light incident on the scene. It is represented as i(x, y). Reflectance is the amount of light reflected by the object in the scene. It is represented by r(x, y).